The nickel exploration boom of the late-1960s and early-1970s
led to the discovery of numerous komatiite-hosted nickel
sulphide deposits, associated with variably serpentinised bodies
of olivine-rich cumulates. Subsequent research has shown the
importance of volcanological processes to understanding the
genesis of these deposits. Crucial developments have come
through consideration of the fluid dynamics of magmas and
magma-crystal mixtures, through observation of the dynamics
and geometry of modern day basaltic lava flows, through
application of theory and experimentation on the kinetics of
crystal growth from magmas, and most importantly from
extensive detailed field mapping of komatiitic sequences in the
Yilgarn Block and elsewhere. From these studies has emerged a
new integrated view of the volcanological setting of
komatiite-hosted deposits, and a recognition that a complete
continuum of deposit types exists. Nevertheless, komatiite associated magmatic nickel deposits
generally fall into two overall types based on the nature of the
sulphide ore. In the first type the bulk of the ore is either massive Fe-Ni-Cu
sulphide or a variable mixture of massive sulphide and an ore
characterised by olivine crystals in a continuous matrix of
sulphide occupying between 30 and 75 per cent by volume of the
rock (called Matrix Ore). Nickel grades of massive sulphide ore
range from 2 - 20 wt% and those of the matrix ore generally fall
in the range 1 - 5 wt% (average 2.5 wt%) Ni/Cu ratios of the
sulphide fraction are generally >10.